#include <stdio.h>
#include <stdlib.h>

struct ListNode 
{
    int val;
    struct ListNode *next;
};

int main()
{
    struct ListNode* n1 = (struct ListNode*)malloc(sizeof(struct ListNode));
    struct ListNode* n2 = (struct ListNode*)malloc(sizeof(struct ListNode));
    struct ListNode* n3 = (struct ListNode*)malloc(sizeof(struct ListNode));
    struct ListNode* n4 = (struct ListNode*)malloc(sizeof(struct ListNode));
    n1->val = 7;
    n2->val = 7;
    n3->val = 7;
    n4->val = 7;
    n1->next = n2;
    n2->next = n3;
    n3->next = n4;
    n4->next = NULL;
    struct ListNode* n = middleNode(n1);
}